1. Field of the Invention
This invention relates to an improvement in a process for hydrogenating activated organonitriles to form the corresponding amines.
2. Description of the Prior Art
The hydrogenation of nitriles to form the corresponding amine is well-known in the prior art. Generally, the hydrogenation is carried out at temperatures of from 50.degree. to 200.degree. C., at pressures of from atmospheric to 3000 psig and in the presence of a hydrogenation catalyst, e.g. Raney nickel or other metal. Activated organonitriles, i.e. those in which the nitrile group has been activated by another group, generally an electron withdrawing group alpha or beta positioned to the nitrile group, have been difficult to reduce. One of the problems in the hydrogenation of these activated organonitriles is that hydrogenation results in the formation of compounds having an amidine linkage. Amidines not only are difficult to reduce to an amine structure, but their presence can influence the hydrogenation reaction and create problems downstream from the reaction, particularly in the separation.
Representative articles relating to the hydrogenation of nitriles include:
U.S. Pat. No. 3,369,002 discloses a process for producing compounds having amidine linkages therein and are produced in equilibrium by the reaction of a nitrile and ammonia.
U.S. Pat. No. 2,049,582 discloses a process for producing amidines by the reaction of a nitrile and an alkali amide. In the discussion of the prior art, the patentee noted that it was difficult to produce amidines in large quantities via the ammonolysis or ammonation of nitriles.
U.S. Pat. No. 2,252,723 discloses a process for producing halogen-alkyl amidines by reacting a haloamidoether with an amine or ammonia.
U.S. Pat. No. 3,733,325 discloses a process for producing aminoethylpiperizine by the catalytic hydrogenation of nitrilotriacetonitrile. Hydrogenation catalysts consisting of nickel or cobalt and optionally containing chromium and copper components are well suited for effecting hydrogenation at temperatures of 75.degree.-200.degree. C. and pressures of 1,000-3,000 psig.
U.S. Pat. No. 3,117,162 discloses a process for producing amines, e.g., propylamine, by the reduction of aliphatic nitriles, the reduction being in the presence of hydrogenation catalysts. Rhodium and platinum on carbon are suggested as hydrogenation catalysts with the hydrogenation being conducted in the liquid phase.